What is the cosmic microwave background theory?
The cosmic microwave background, or CMB, is the faint glow of radiation left over from the Big Bang, when the universe was just 380,000 years old and cooled enough for atoms to form. It fills all of space at a temperature of about 2.7 Kelvin. My team on COBE measured its spectrum to be a perfect blackbody, confirming the Big Bang model, and then we found the tiny temperature fluctuations—at the level of one part in 100,000—that represent density variations. These variations, amplified by gravity over billions of years, grew into the galaxies and clusters we see today. As I like to say, 'We are all made of star stuff,' but the CMB tells us how that star stuff got its start.
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